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FreeBSD-EN-20:14.linuxkpi                                       Errata Notice
                                                          The FreeBSD Project

Topic:          Kernel panic in LinuxKPI subsystem

Category:       core
Module:         linuxkpi
Announced:      2020-07-08
Affects:        FreeBSD 12.1 and 11.3
Corrected:      2020-01-22 00:30:27 UTC (stable/12, 12.1-STABLE)
                2020-07-08 19:57:24 UTC (releng/12.1, 12.1-RELEASE-p7)
                2020-01-22 15:51:24 UTC (stable/11, 11.3-STABLE)
                2020-07-08 19:57:24 UTC (releng/11.3, 11.3-RELEASE-p11)

Note: FreeBSD 11.4 was branched after the original commit to the stable/11
branch and already includes this erratum.

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.FreeBSD.org/>.

0.   Revision history

v1.0   Initial release.
v1.1   Correct typo in patch URL.

I.   Background

The LinuxKPI subsystem allows kernel code ported from Linux to run in the
FreeBSD kernel without extensive modification.  Some graphics drivers make
use of this subsystem.

II.  Problem Description

A bug in one of the LinuxKPI subroutines could cause a kernel panic.

III. Impact

Certain graphical applications may trigger a kernel panic.  This is most
often observed when using X11 forwarding to run an application remotely.

IV.  Workaround

No workaround is available.

V.   Solution

Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date and reboot.

Perform one of the following:

1) To update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install
# shutdown -r +10min "Rebooting for errata update"

2) To update your system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/EN-20:14/linuxkpi.patch
# fetch https://security.FreeBSD.org/patches/EN-20:14/linuxkpi.patch.asc
# gpg --verify linuxkpi.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/12/                                                        r356953
releng/12.1/                                                      r363023
stable/11/                                                        r356987
releng/11.3/                                                      r363023
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<other info on the problem>

<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242913>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-20:14.linuxkpi.asc>
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